(x+5)(x-3)=15

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Solution for (x+5)(x-3)=15 equation:


Simplifying
(x + 5)(x + -3) = 15

Reorder the terms:
(5 + x)(x + -3) = 15

Reorder the terms:
(5 + x)(-3 + x) = 15

Multiply (5 + x) * (-3 + x)
(5(-3 + x) + x(-3 + x)) = 15
((-3 * 5 + x * 5) + x(-3 + x)) = 15
((-15 + 5x) + x(-3 + x)) = 15
(-15 + 5x + (-3 * x + x * x)) = 15
(-15 + 5x + (-3x + x2)) = 15

Combine like terms: 5x + -3x = 2x
(-15 + 2x + x2) = 15

Solving
-15 + 2x + x2 = 15

Solving for variable 'x'.

Reorder the terms:
-15 + -15 + 2x + x2 = 15 + -15

Combine like terms: -15 + -15 = -30
-30 + 2x + x2 = 15 + -15

Combine like terms: 15 + -15 = 0
-30 + 2x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '30' to each side of the equation.
-30 + 2x + 30 + x2 = 0 + 30

Reorder the terms:
-30 + 30 + 2x + x2 = 0 + 30

Combine like terms: -30 + 30 = 0
0 + 2x + x2 = 0 + 30
2x + x2 = 0 + 30

Combine like terms: 0 + 30 = 30
2x + x2 = 30

The x term is 2x.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2x + 1 + x2 = 30 + 1

Reorder the terms:
1 + 2x + x2 = 30 + 1

Combine like terms: 30 + 1 = 31
1 + 2x + x2 = 31

Factor a perfect square on the left side:
(x + 1)(x + 1) = 31

Calculate the square root of the right side: 5.567764363

Break this problem into two subproblems by setting 
(x + 1) equal to 5.567764363 and -5.567764363.

Subproblem 1

x + 1 = 5.567764363 Simplifying x + 1 = 5.567764363 Reorder the terms: 1 + x = 5.567764363 Solving 1 + x = 5.567764363 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = 5.567764363 + -1 Combine like terms: 1 + -1 = 0 0 + x = 5.567764363 + -1 x = 5.567764363 + -1 Combine like terms: 5.567764363 + -1 = 4.567764363 x = 4.567764363 Simplifying x = 4.567764363

Subproblem 2

x + 1 = -5.567764363 Simplifying x + 1 = -5.567764363 Reorder the terms: 1 + x = -5.567764363 Solving 1 + x = -5.567764363 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = -5.567764363 + -1 Combine like terms: 1 + -1 = 0 0 + x = -5.567764363 + -1 x = -5.567764363 + -1 Combine like terms: -5.567764363 + -1 = -6.567764363 x = -6.567764363 Simplifying x = -6.567764363

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.567764363, -6.567764363}

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